Project 3: Continuous Wave Electron Paramagnetic Resonance Imaging.This technique provides non-invasive assessment of tissue/tumor redox status using redox sensitive paramagnetic contrast agents called nitroxides. We have now examining new molecules as reporters of oxidative stress, which are precursors of nitroxides and are converted to the corresponding nitroxide by oxidation with reactive oxygen species. Such oxidation should provide information on tissue oxidative stress. Instrumentation is also being developed to provide detection at higher frequencies to give enhanced sensitivity and spatial resolution.